1. Field of the Invention
The present invention relates to a stabilizer bushing for a vehicle and a method for producing the stabilizer bushing. More particularly, the present invention relates to a stabilizer bushing for a vehicle that is inclinedly attached to a vehicle body to support a stabilizer bar on the vehicle body in a vibration damping fashion and an advantageous method for producing such a stabilizer bushing for a vehicle.
2. Description of Related Art
As is well known, a stabilizer bar is mounted on a vehicle such as an automobile for the purpose of suppressing tilting of a vehicle body that occurs when the vehicle makes a turn or the like. Generally, the stabilizer bar is supported on a vehicle body in a vibration damping fashion via a stabilizer bushing (vibration damping bushing). The stabilizer bushing includes a bushing body that is made of a cylindrical rubber elastic body having an inner bore into which a stabilizer bar is inserted and a bracket mounted on an outer peripheral portion of the bushing body for attaching to a vehicle body such as a body or a frame of a vehicle. Usually, such a bracket is configured to include a mounting portion mounted on the outer peripheral portion of the bushing body and an attachment portion integrally formed in a manner extending out from two ends of the mounting portion in directions perpendicular to an axial direction of the bushing body and attached to the vehicle body. Further, the attachment portion is provided with two attachment surfaces extending parallel to each other. The bushing body is attached to a vehicle body by attaching the attachment portion to the vehicle in a state in which the two attachment surfaces are superimposed on the vehicle body.
A kind of such a stabilizer bushing is known having a structure in which two partition members are embedded in a middle portion in a direction perpendicular to an axial direction of the bushing body in a manner partitioning the stabilizer bushing into an inner rubber portion positioned on a more inner side than the partition members and an outer rubber portion positioned on a more outer side than the partition members, the partition members each having a semi-tubular shape with a circular arc-shaped cross section and being rigid. Conventionally, such a structure having two partition members embedded in a bushing body is frequently adopted in a stabilizer bushing that implements measures to prevent the occurrence of stick-slip.
For example, Japanese Utility Model Application Laid-Open Publication No. SHO 61-134411 (Related Art 1) discloses a structure in which two partition members are embedded in a bushing body in a stabilizer bushing that prevents the occurrence of stick-slip by fixing a sliding member made of a liner cloth and the like having surface lubricity to an inner circumferential surface of the bushing body to reduce frictional resistance between the bushing body and a stabilizer bar. In this case, due to the presence of the two partition members, elastic deformation of the inner rubber portion of the bushing body during vibration input is essentially prevented, thereby preventing occurrence of problems such as peeling of the sliding member due to the deformation of the inner circumferential surface of the bushing body. A stabilizer bushing having a structure in which two partition members are embedded in a bushing body is also disclosed in Japanese Patent Laid-Open Publication No. 2008-201307 (Relate Art 2) and the like.
However, according to a research conducted by the inventors of the present invention, it is found that it is difficult to adequately ensure operation stability and good riding comfort when a conventional stabilizer bushing having two partition members embedded in a bushing body is attached to a vehicle body in an inclined state with respect to the vehicle body. That is, it is found that, as compared to the case where a bushing body is attached to a vehicle body in a state of being horizontally arranged with respect to the vehicle body, operation stability decreases and riding comfort deteriorates in the case where the bushing body is attached to the vehicle body in a state of being inclinedly arranged with respect to the vehicle body by rotating the stabilizer bushing about a central axis for a predetermined angle and attaching the attachment portion of the bracket to the vehicle body in a state in which the two attachment surfaces of the attachment portion are superimposed on the vehicle body while being kept inclined with respect to a horizontal direction.    [Related Art 1] Japanese Utility Model Application Laid-Open Publication No. SHO 61-134411    [Related Art 2] Japanese Patent Laid-Open Publication No. 2008-201307